Exhaust gas treatment device and exhaust gas treatment method

ABSTRACT

An exhaust gas treatment device includes an exhaust gas line through which a combustion exhaust gas discharged from a power generation facility flows, a waste heat recovery boiler recovering waste heat of the combustion exhaust gas, a branch exhaust gas line provided to be connected between a front stage and a downstream stage of the waste heat recovery boiler on a main exhaust gas line, a nitrogen oxide removal unit removing nitrogen oxide in an integrated combustion exhaust gas into which a combustion exhaust gas flowing through the main exhaust gas line and a combustion exhaust gas flowing through the branch exhaust gas line are integrated, an integrated waste heat recovery boiler recovering waste heat of the integrated combustion exhaust gas from which nitrogen oxide has been removed, and a CO2 recovery unit recovering CO2 in the integrated combustion exhaust gas.

TECHNICAL FIELD

The present invention relates to an exhaust gas treatment device and anexhaust gas treatment method, and for example, relates to an exhaust gastreatment device and an exhaust gas treatment method for treatingcombustion exhaust gas exhausted from a power generation facility or thelike.

BACKGROUND ART

In the past, there has been proposed an exhaust gas treatment deviceincluding a plurality of exhaust gas flow paths which are connected to aplurality of gas turbines and includes a waste heat recovery boilerrecovering waste heat of combustion exhaust gas discharged from the gasturbines (see Patent Document 1, for example). In the exhaust gastreatment device, the waste heat of the combustion exhaust gasdischarged from each gas turbine is recovered by the waste heat recoveryboiler provided to each exhaust gas flow path. Then, the combustionexhaust gas, from which the waste heat has been recovered, in each ofthe exhaust gas flow paths is integrated into an integrated combustionexhaust gas, and thereafter, carbon dioxide (CO₂) in the integratedcombustion exhaust gas is recovered by a CO₂ absorbing liquid in a CO₂recovery device.

CITATION LIST Patent Documents

Patent Document 1: JP 5291449 B

SUMMARY OF INVENTION Problem to be Solved by the Invention

Here, in the exhaust gas treatment device, a component derived fromnitrogen oxide contained in the combustion exhaust gas (for example,nitrogen dioxide (NO₂)) accumulates as an accumulated component in theCO₂ absorbing liquid, and therefore, it is preferable to provide anitrogen oxide removal device for removing nitrogen oxide in the exhaustgas on a front stage of the carbon dioxide recovery device. The nitrogenoxide removal device needs to be provided on a front stage of a wasteheat recovery device in order to efficiently remove nitrogen oxide,because a nitrogen oxide removal efficiency decreases when a temperatureof the exhaust gas decreases to lower than a predetermined temperature(for example, less than 300° C.). However, in the exhaust gas treatmentdevice including a plurality of exhaust gas flow paths connected to aplurality of gas turbines, the nitrogen oxide removal device needs to beprovided on a front stage of the waste heat recovery boiler of eachexhaust gas flow path, and the exhaust gas treatment device may increasein size, thus increasing facility cost.

The present invention has an object to provide an exhaust gas treatmentdevice and an exhaust gas treatment method capable of reducing anaccumulation amount of the nitrogen oxide-derived component in the CO₂absorbing liquid and capable of reducing the increase in the facilitycost.

Solution to Problem

An exhaust gas treatment device according to the present inventionincludes: a first exhaust gas flow path through which a first combustionexhaust gas discharged from a power generation facility flows; a wasteheat recovery unit provided to the first exhaust gas flow path andrecovers waste heat of the first combustion exhaust gas; a secondexhaust gas flow path branched from the first exhaust gas flow path andprovided between a front stage and downstream stage of the waste heatrecovery unit on the first exhaust gas flow path, in which at least apart of the first combustion exhaust gas flowing through the firstexhaust gas flow path flows, as a second combustion exhaust gas, throughthe second exhaust gas flow path; a nitrogen oxide removal unitconfigured to remove nitrogen oxide in an integrated combustion exhaustgas into which the first combustion exhaust gas and the secondcombustion exhaust gas are integrated, the first combustion exhaust gasflowing through the first exhaust gas flow path with the waste heat ofthe first combustion exhaust gas having been recovered by the waste heatrecovery unit, and the second combustion exhaust gas flowing through thesecond exhaust gas flow path with a temperature of the second combustionexhaust gas being higher relative to the first combustion exhaust gas;an integrated waste heat recovery unit configured to recover waste heatof the integrated combustion exhaust gas with the nitrogen oxide havingbeen removed by the nitrogen oxide removal unit; and a CO₂ recovery unitconfigured to recover CO₂ in the integrated combustion exhaust gas by aCO₂ absorbing liquid with the waste heat of the integrated combustionexhaust gas having been recovered by the integrated waste heat recoveryunit.

According to this configuration, the combustion exhaust gas dischargedfrom the power generation facility is branched into the first exhaustgas flow path and the second exhaust gas flow path, and thereafter, thewaste heat of the first combustion exhaust gas flowing through the firstexhaust gas flow path is recovered by the waste heat recovery unit,while the first combustion exhaust gas is integrated with the secondcombustion exhaust gas flowing through the second exhaust gas flow pathin a state of the temperature thereof being higher relative to the firstcombustion exhaust gas from which the waste heat has been recovered bythe waste heat recovery unit, and then, the integrated combustionexhaust gas is resulted. This can adjust the temperature of theintegrated combustion exhaust gas introduced into the nitrogen oxideremoval unit to a range suitable for decomposing and removing nitrogenoxide, such that nitrogen oxide in the combustion exhaust gas dischargedfrom the power generation facility can be efficiently removed. Since thetemperature of the integrated combustion exhaust gas can be adjusted tobe in a range suitable for decomposing and removing nitrogen oxide onlyby providing the second exhaust gas flow path, the increase in thefacility cost can be also reduced. Therefore, the exhaust gas treatmentdevice can be achieved in which nitrogen oxide can be efficientlyremoved and the increase in the facility cost can be reduced.

The exhaust gas treatment device according to the present inventionpreferably further includes a control unit that adjusts a flow rate ofthe first combustion exhaust gas flowing through the first exhaust gasflow path and a flow rate of the second combustion exhaust gas flowingthrough the second exhaust gas flow path to control such that atemperature of the integrated combustion exhaust gas introduced into thenitrogen oxide removal unit is 300° C. or higher and 400° C. or lower.This configuration enables the gas temperature of the integratedcombustion exhaust gas introduced into the nitrogen oxide removal unitto be 300° C. or higher and 400° C. or lower that is suitable fordecomposition treatment of nitrogen oxide, such that the accumulationamount of the nitrogen oxide-derived component in the CO₂ absorbingliquid in the CO₂ recovery unit can be efficiently reduced.

An exhaust gas treatment device according to the present inventionincludes a first exhaust gas flow path through which a first combustionexhaust gas discharged from a first power generation facility flows; asecond exhaust gas flow path through which a second combustion exhaustgas discharged from a second power generation facility flows; a wasteheat recovery unit that is provided to the first exhaust gas flow pathand recovers waste heat of the first combustion exhaust gas; a nitrogenoxide removal unit configured to remove nitrogen oxide in an integratedcombustion exhaust gas into which the first combustion exhaust gas andthe second combustion exhaust gas are integrated, the first combustionexhaust gas flowing through the first exhaust gas flow path with thewaste heat of the first combustion exhaust gas having been recovered bythe waste heat recovery unit, and the second combustion exhaust gasflowing through the second exhaust gas flow path with a temperature ofthe second combustion exhaust gas being higher relative to the firstcombustion exhaust gas; an integrated waste heat recovery unitconfigured to recover waste heat of the integrated combustion exhaustgas with the nitrogen oxide having been removed by the nitrogen oxideremoval unit; and a CO₂ recovery unit that recovers CO₂ in theintegrated combustion exhaust gas by a CO₂ absorbing liquid with thewaste heat of the integrated combustion exhaust gas having beenrecovered by the integrated waste heat recovery unit.

According to this configuration, the waste heat of the first combustionexhaust gas discharged from the first power generation facility isrecovered by the waste heat recovery unit, while the first combustionexhaust gas is integrated with the second combustion exhaust gas flowingthrough the second exhaust gas flow path in a state of the temperaturethereof being higher relative to the first combustion exhaust gas fromwhich the waste heat has been recovered by the waste heat recovery unit,and then, the integrated combustion exhaust gas is resulted. This canadjust the temperature of the integrated combustion exhaust gasintroduced into the nitrogen oxide removal unit to a range suitable fordecomposing and removing nitrogen oxide, such that nitrogen oxide in thecombustion exhaust gas discharged from the power generation facility canbe efficiently removed. Since nitrogen oxide in the integratedcombustion exhaust gas can be efficiently removed without providing thewaste heat recovery unit to the second exhaust gas flow path, theincrease in the facility cost can be also reduced. Therefore, theexhaust gas treatment device can be achieved in which nitrogen oxide canbe efficiently removed and the increase in the facility cost can bereduced.

The exhaust gas treatment device according to the present inventionpreferably further includes a control unit configured to adjust a flowrate of each of the combustion exhaust gases flowing through the firstexhaust gas flow path and the second exhaust gas flow path to controlsuch that a temperature of the integrated combustion exhaust gasintroduced into the nitrogen oxide removal unit is 300° C. or higher and400° C. or lower. This configuration enables the gas temperature of theintegrated combustion exhaust gas introduced into the nitrogen oxideremoval unit to be 300° C. or higher and 400° C. or lower that issuitable for decomposition treatment of nitrogen oxide, such that theaccumulation amount of the nitrogen oxide-derived component in the CO₂absorbing liquid in the CO₂ recovery unit can be efficiently reduced.

In the exhaust gas treatment device according to the present invention,the nitrogen oxide removal unit is preferably provided within theintegrated waste heat recovery unit. This configuration enables theintegrated waste heat recovery unit and the nitrogen oxide removal unitto be formed into one body, and therefore, facilities of the exhaust gastreatment device can be reduced in size and simplified.

In the exhaust gas treatment device according to the present invention,the nitrogen oxide removal unit preferably includes a reducing agentinjection unit configured to inject a nitrogen oxide removal catalystremoving the nitrogen oxide and a reducing agent. According to thisconfiguration, the reducing agent and the nitrogen oxide removalcatalyst enable nitrogen oxide contained in the integrated combustiongas to be further more efficiently decomposed and removed.

The exhaust gas treatment device according to the present inventionpreferably further includes: a control unit configured to control asupply amount of the reducing agent, based on a gas flow rate andnitrogen oxide concentration of the integrated combustion exhaust gasintroduced into the CO₂ recovery unit. This configuration enablesnitrogen oxide in the integrated combustion exhaust gas introduced intothe CO₂ recovery unit to be easily controlled to be in a desiredconcentration range.

In the exhaust gas treatment device according to the present invention,the integrated waste heat recovery unit preferably generates a CO₂compression portion-driving steam for compressing CO₂ discharged fromthe CO₂ recovery unit by using the waste heat of the integratedcombustion exhaust gas with the nitrogen oxide having been removed, andsupplies the generated CO₂ compression portion-driving steam to a CO₂compression portion. This configuration makes it possible to effectivelyutilize the waste heat of the integrated combustion exhaust gas as theCO₂ compression portion-driving steam, and therefore, an operation costof the exhaust gas treatment device can be reduced.

In the exhaust gas treatment device according to the present invention,the integrated waste heat recovery unit preferably generates aturbine-driving steam by using the waste heat of the integratedcombustion exhaust gas with the nitrogen oxide having been removed, andsupplies the generated turbine-driving steam to a steam turbine. Thisconfiguration makes it possible to effectively utilize the waste heat ofthe integrated combustion exhaust gas as the turbine-driving steam, andtherefore, an operation cost of the exhaust gas treatment device can bereduced.

The exhaust gas treatment device according to the present inventionpreferably includes a heating unit configured to heat the integratedcombustion exhaust gas provided on a front stage of the nitrogen oxideremoval unit, the integrated waste heat recovery unit generates theturbine-driving steam by using the waste heat of the integratedcombustion exhaust gas heated by the heating unit, and supplies thegenerated turbine-driving steam to the steam turbine. This configurationmakes it possible to effectively utilize the waste heat of theintegrated combustion exhaust gas as the turbine-driving steam, andtherefore, an operation cost of the exhaust gas treatment device can bereduced. The heating unit can also adjust the temperature of theintegrated combustion exhaust gas introduced into the integrated wasteheat recovery unit to a desired temperature range.

In the exhaust gas treatment device according to the present invention,a control unit is preferably configured to measure the temperature andgas flow rate of the integrated combustion exhaust gas introduced intothe nitrogen oxide removal unit, and controls at least one of an amountof a fuel supplied to a combustor in the power generation facility andan amount of the steam supplied to the steam turbine, based on themeasured temperature and gas flow rate. This configuration enablescontrol of the temperature and flow rate of the integrated combustionexhaust gas introduced into the nitrogen oxide removal unit to be in adesired range.

In the exhaust gas treatment device according to the present invention,the power generation facility preferably includes an existing powergeneration facility. According to this configuration, the temperature ofthe integrated combustion exhaust gas can be adjusted to be in a rangesuitable for decomposing and removing nitrogen oxide by also providingthe first gas flow path and the second gas flow path to the existingpower generation facility, and thus the increase in the facility costcan be also reduced.

An exhaust gas treatment method according to the present inventionincludes the steps of: removing nitrogen oxide in an integratedcombustion exhaust gas into which a first combustion exhaust gas and asecond combustion exhaust gas are integrated, the first combustionexhaust gas being discharged from a power generation device with wasteheat of the first combustion exhaust gas having been recovered by awaste heat recovery unit which is provided to a first exhaust gas flowpath, and the second combustion exhaust gas flowing through a secondexhaust gas flow path which is provided to be connected between a frontstage and a downstream stage of the waste heat recovery unit on thefirst exhaust gas flow path with a temperature of the second combustionexhaust gas being higher relative to the first combustion exhaust gasfrom which the waste heat has been recovered by the waste heat recoveryunit; recovering waste heat of the integrated combustion exhaust gaswith the nitrogen oxide having been removed; and recovering CO₂ in theintegrated combustion exhaust gas by a CO₂ absorbing liquid, the wasteheat of the integrated combustion exhaust gas having been recovered.

According to this method, the waste heat of the first combustion exhaustgas flowing through the first exhaust gas flow path is recovered by thewaste heat recovery unit, while the first combustion exhaust gas isintegrated with the second combustion exhaust gas flowing through thesecond exhaust gas flow path in a state of the temperature thereof beinghigher relative to the first combustion exhaust gas from which the wasteheat has been recovered by the waste heat recovery unit, and then, theintegrated combustion exhaust gas is resulted. This can adjust thetemperature of the integrated combustion exhaust gas to a range suitablefor decomposing and removing nitrogen oxide, such that nitrogen oxide inthe combustion exhaust gas discharged from the power generation facilitycan be efficiently removed. Since nitrogen oxide in the combustionexhaust gas discharged from the power generation facility can beefficiently removed without providing the nitrogen oxide removal unit tothe second exhaust gas flow path, the increase in the facility cost canbe also reduced. Therefore, the exhaust gas treatment device can beachieved in which nitrogen oxide can be efficiently removed and theincrease in the facility cost can be reduced.

An exhaust gas treatment method according to the present inventionincludes: removing nitrogen oxide in an integrated combustion exhaustgas into which a first combustion exhaust gas and a second combustionexhaust gas are integrated, the first combustion exhaust gas beingdischarged from a first power generation device with waste heat of thefirst combustion exhaust gas having been recovered by a waste heatrecovery unit which is provided to a first exhaust gas flow path, andthe second combustion exhaust gas being discharged from a second powergeneration device and flowing through a second exhaust gas flow pathwith a temperature of the second combustion exhaust gas being higherrelative to the first combustion exhaust gas from which the waste heathas been recovered by the waste heat recovery unit; removing nitrogenoxide in the integrated combustion exhaust gas into which combustionexhaust gases are integrated, the combustion exhaust gases beingdischarged and flowing through a plurality of exhaust gas flow paths atleast one of which is provided with a waste heat recovery unit thatrecovers waste heat of the combustion exhaust gas; recovering waste heatof the integrated combustion exhaust gas with the nitrogen oxide havingbeen removed; and recovering CO₂ in the integrated combustion exhaustgas by a CO₂ absorbing liquid, the waste heat of the integratedcombustion exhaust gas having been recovered.

According to this method, the waste heat of the first combustion exhaustgas discharged from the first power generation facility is recovered bythe waste heat recovery unit, while the first combustion exhaust gas isintegrated with the second combustion exhaust gas flowing through thesecond exhaust gas flow path in a state of the temperature thereof beinghigher relative to the first combustion exhaust gas from which the wasteheat has been recovered by the waste heat recovery unit, and then, theintegrated combustion exhaust gas is resulted. This can adjust thetemperature of the integrated combustion exhaust gas to a range suitablefor decomposing and removing nitrogen oxide, such that nitrogen oxide inthe combustion exhaust gas discharged from the power generation facilitycan be efficiently removed. Since nitrogen oxide in the integratedcombustion exhaust gas can be efficiently removed without providing thewaste heat recovery unit to the second exhaust gas flow path, theincrease in the facility cost can be also reduced. Therefore, theexhaust gas treatment device can be achieved in which nitrogen oxide canbe efficiently removed and the increase in the facility cost can bereduced.

Advantageous Effect of Invention

According to this method, an exhaust gas treatment device and an exhaustgas treatment method can be achieved which are capable of reducing theaccumulation amount of the nitrogen oxide-derived component in the CO₂absorbing liquid and capable of reducing the increase in the facilitycost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of an exhaust gastreatment device according to a first embodiment.

FIG. 2 is a schematic diagram of a power generation facility accordingto the first embodiment.

FIG. 3 is a schematic diagram illustrating another example of theexhaust gas treatment device according to the first embodiment.

FIG. 4 is a schematic diagram illustrating another example of theexhaust gas treatment device according to the first embodiment.

FIG. 5 is a schematic diagram illustrating an example of an exhaust gastreatment device according to a second embodiment.

FIG. 6 is a schematic view illustrating another example of the exhaustgas treatment device according to the second embodiment.

FIG. 7 is a graph illustrating an accumulation amount of a nitrogenoxide-derived component in a CO₂ absorbing liquid in an exhaust gastreatment device according to an example and a comparative example.

DESCRIPTION OF EMBODIMENTS

The present inventors have focused on a matter that, according to anexhaust gas treatment device of related art, in order to efficientlyremove nitrogen oxide in the combustion exhaust gas, a temperature ofthe combustion exhaust gas introduced into a nitrogen oxide removal unitneeds to be kept at high temperature (for example, 300° C. or higher and400° C. or lower), while the facility cost increases in a case where thenitrogen oxide removal unit is provided on a front stage of each ofwaste heat recovery units in a plurality of exhaust gas flow paths.Then, the present inventors have conceived an idea of dividing andcausing the combustion exhaust gas discharged from the power generationfacility to flow as a first combustion exhaust gas from which the wasteheat has been recovered by the waste heat recovery unit and a secondcombustion exhaust gas from which the waste heat has not been recoveredand of which a temperature is higher than the first combustion exhaustgas, and thereafter, integrating the first combustion exhaust gas andthe second combustion exhaust gas into an integrated combustion exhaustgas to be introduced into the nitrogen oxide removal unit. From thisidea, the present inventors have found that it is possible to make a gastemperature of the integrated combustion exhaust gas a temperaturesuitable for decomposing and removing nitrogen oxide, reduce anaccumulation amount of a nitrogen oxide-derived component in a CO₂absorbing liquid in a CO₂ recovery unit, and reduce increase in thefacility cost, and completed the present invention.

Hereinafter, embodiments of the present invention will be described indetail while referring to the attached drawings. Note that the presentinvention is not limited to the following embodiments and the presentinvention can be carried out by applying suitable modifications.

First Embodiment

FIG. 1 is a schematic view illustrating an example of an exhaust gastreatment device 1 according to a first embodiment of the presentinvention. As illustrated in FIG. 1, the exhaust gas treatment device 1according to the present embodiment recovers, by a waste heat recoveryboiler 11 and an integrated waste heat recovery boiler 12, waste heat ofa combustion exhaust gas G₁₁ discharged from a power generation facility10 generating the combustion exhaust gas G₁₁, and thereafter, recoversCO₂ contained in an integrated combustion exhaust gas G₂₁ by a CO₂recovery unit 13. The exhaust gas treatment device 1 includes the powergeneration facility 10 discharging the combustion exhaust gas G₁₁, thewaste heat recovery boiler 11 provided on a downstream stage of thepower generation facility 10 in a flow direction of the combustionexhaust gas G₁₁, the integrated waste heat recovery boiler 12 providedon a downstream stage of the waste heat recovery boiler 11, the CO₂recovery unit 13 provided on a downstream stage of the integrated wasteheat recovery boiler 12, and a CO₂ compression portion 14 provided on adownstream stage of the CO₂ recovery unit 13. A stack 15 discharging apart of the combustion exhaust gas G₁₁ is provided between the wasteheat recovery boiler 11 and the integrated waste heat recovery boiler12.

FIG. 2 is a schematic view of the power generation facility 10 accordingto the present embodiment. As illustrated in FIG. 2, the powergeneration facility 10 is a single-shaft type combined power generationfacility (gas turbine combined cycle) in which a gas turbine 210, asteam turbine 220, and a generator 230 are configured in one shaft. Thegas turbine 210 includes a compressor 211 that compresses an air A, acombustor 212 that combusts a fuel F with the air A compressed by thecompressor 211, and a turbine 213 that is rotationally driven by acombustion gas generated in the combustor 212. The compressor 211 isconnected to the turbine 213 via a turbine shaft 240.

The steam turbine 220 includes a low-pressure steam turbine 221 that isrotationally driven by a low-pressure steam, and amedium-pressure/high-pressure steam turbine 222 in which a mid-pressuresteam turbine 222A that is rotationally driven by a medium-pressuresteam is connected to a high-pressure steam turbine 222B that isrotationally driven by a high-pressure steam. The low-pressure steamturbine 221 and the medium-pressure/high-pressure steam turbine 222 areconnected to the generator 230 and the gas turbine 210 via the turbineshaft 240. The generator 230 generates power by the rotational drive ofthe gas turbine 210 and the steam turbine 220 via the turbine shaft 240.

The power generation facility 10 supplies the combustion exhaust gas G₁₁generated by the power generation to the waste heat recovery boiler 11via an exhaust gas line L₁₁. The exhaust gas line L₁₁ is provided with abranch exhaust gas line L_(11B) between a front stage and a downstreamstage of the waste heat recovery boiler 11 in the exhaust gas line L₁₁,the branch exhaust gas line L_(11B) branching from the exhaust gas lineL₁₁. Specifically, in the present embodiment, the exhaust gas line L₁₁is branched into a main exhaust gas line (first exhaust gas flow path)L_(11A) and a branch exhaust gas line (second exhaust gas flow path)L_(11B) between the front stage and the downstream stage of the wasteheat recovery boiler 11.

The exhaust gas line L₁₁ is provided with a flow rate control valveV_(11A), the waste heat recovery boiler 11, and the stack 15 in thisorder. The flow rate control valve V_(11A) adjusts a flow rate of thecombustion exhaust gas (first combustion exhaust gas) G_(11A) flowingthrough the main exhaust gas line L_(11A). The waste heat recoveryboiler 11 recovers the waste heat of the combustion exhaust gas G_(11A)flowing through the main exhaust gas line L_(11A), and supplies thecombustion exhaust gas G_(11A) from which the waste heat has beenrecovered to the stack 15. The stack 15 discharges a part of thecombustion exhaust gas G_(11A) to outside as needed, and supplies thecombustion exhaust gas G_(11A) to the integrated waste heat recoveryboiler 12. The branch exhaust gas line L_(11B) is provided with a flowrate control valve V_(11B). The flow rate control valve Vim adjusts aflow rate of the combustion exhaust gas (second combustion exhaust gas)G_(11B) flowing through the branch exhaust gas line L_(11B). The branchexhaust gas line L_(11B) supplies a part or all of the combustionexhaust gas G₁₁ flowing through the exhaust gas line L₁₁ to theintegrated waste heat recovery boiler 12 without using the waste heatrecovery boiler 11 and the stack 15.

The integrated waste heat recovery boiler 12 is supplied with theintegrated combustion exhaust gas G₂₁ in which the combustion exhaustgas G_(11A) flowing through the main exhaust gas line L_(11A) and thecombustion exhaust gas G_(11B) flowing through the branch exhaust gasline L_(11B) are integrated. The integrated waste heat recovery boiler12 recovers the waste heat of the integrated combustion exhaust gas G₂₁.The integrated waste heat recovery boiler 12 is provided with, withinthereof, a nitrogen oxide removal unit 120 that reduces and removesnitrogen oxide such as nitrogen monoxide and nitrogen dioxide containedin the integrated combustion exhaust gas G₂₁. In this way, by providingthe nitrogen oxide removal unit 120 within the integrated waste heatrecovery boiler 12, the exhaust gas treatment device 1 can be reduced insize. Note that the nitrogen oxide removal unit 120 may not benecessarily provided in an integrated form with the integrated wasteheat recovery boiler 12, and may be provided outside the integratedwaste heat recovery boiler 12.

The nitrogen oxide removal unit 120 includes a reducing agent supplyunit 121 that injects a reducing agent into the integrated combustionexhaust gas G₂₁ to reduce nitrogen oxide, and a selective catalyticreduction (SCR) unit 122 that is provided on a downstream stage of thereducing agent supply unit 121 and filled with a DeNOx catalystselectively reducing nitrogen oxide. The reducing agent in the reducingagent supply unit 121 is not specifically limited so long as it candecompose and remove nitrogen oxide such as nitrogen monoxide andnitrogen dioxide. The DeNOx catalyst in the selective catalyticreduction unit 122 is not specifically limited so long as it candecompose and remove nitrogen oxide such as nitrogen monoxide andnitrogen dioxide.

The integrated waste heat recovery boiler 12, in the nitrogen oxideremoval unit 120, supplies the reducing agent from the reducing agentsupply unit 121 to the integrated combustion exhaust gas G₂₁, andperforms a decomposition treatment by the selective catalytic reductionunit 122 on nitrogen oxide supplied with the reducing agent. Theintegrated waste heat recovery boiler 12 recovers the waste heat of theintegrated combustion exhaust gas G₂₁ of which nitrogen oxide hasundergone the decomposition treatment, and supplies the integratedcombustion exhaust gas G₂₁ from which the waste heat has been recoveredto the CO₂ recovery unit 13.

The CO₂ recovery unit 13 includes a CO₂ absorbing tower that recoverscarbon dioxide (CO₂) in the integrated combustion exhaust gas G₂₁ by theCO₂ absorbing liquid, and a CO₂ regeneration tower that heats the CO₂absorbing liquid having absorbed CO₂ to release CO₂ from the CO₂absorbing liquid. A CO₂ absorbing liquid is not specifically limited solong as it can recover carbon dioxide (CO₂) in the integrated combustionexhaust gas G₂₁, and an amine series absorbing liquid can be used, forexample. The CO₂ recovery unit 13 discharges, to outside, the integratedcombustion exhaust gas G₂₁ from which CO₂ has been recovered, andsupplies the recovered CO₂ to the CO₂ compression portion 14. The CO₂compression portion 14 compresses and discharges CO₂ supplied from theCO₂ recovery unit 13.

The exhaust gas treatment device 1 includes a first exhaust gasmeasurement unit 16 that measures a gas flow rate and temperature of theintegrated combustion exhaust gas G₂₁ introduced into the integratedwaste heat recovery boiler 12, a second exhaust gas measurement unit 17that measures a gas flow rate and nitrogen oxide concentration of theintegrated combustion exhaust gas G₂₁ introduced into the CO₂ recoveryunit 13, and a control unit 18 that controls a supply amount of a fuel Fsupplied to the power generation facility 10 and a supply amount of thereducing agent supplied from the reducing agent supply unit 121 to theintegrated combustion exhaust gas G₂₁. The control unit 18 adjustsopening amounts of the flow rate control valves V_(11A) and V_(11B), andthe supply amount of the fuel supplied to the power generation facility10, based on the gas flow rate and temperature of the integratedcombustion exhaust gas G₁ measured by the first exhaust gas measurementunit 16. The control unit 18 controls the supply amount of the fuel Fsupplied to the power generation facility 10, based on the gas flow rateand nitrogen oxide concentration of the integrated combustion exhaustgas G₁ measured by the second exhaust gas measurement unit 17. Themeasurement of the gas flow rate and the temperature by the firstexhaust gas measurement unit 16, and the measurement of the gas flowrate and the nitrogen oxide concentration by the second exhaust gasmeasurement unit 17 are performed using a publicly known method ofrelated art.

The control unit 18 adjusts the opening amounts of the flow rate controlvalves V_(11A) and V_(11B), and the supply amount of the fuel F suppliedto the power generation facility 10 to control such that the temperatureof the integrated combustion exhaust gas G₂₁ measured by the firstexhaust gas measurement unit 16 is 300° C. or higher and 400° C. orlower. By such control, the exhaust gas treatment device 1 can make thetemperature of the integrated combustion exhaust gas G₂₁ supplied to thenitrogen oxide removal unit 120 in the integrated waste heat recoveryboiler 12 a temperature suitable for decomposing and removing nitrogenoxide, so that nitrogen oxide in the integrated combustion exhaust gasG₂₁ can be further more efficiently decomposed and removed.

In a case where the temperature of the integrated combustion exhaust gasG₂₁ measured by the first exhaust gas measurement unit 16 is lower than300° C., the control unit 18 controls at least one of the opening amountof the flow rate control valve V_(11A) to be decreased and the openingamount of the flow rate control valve V_(11B) to be increased, so that aratio, in the integrated combustion exhaust gas G₂₁, of the combustionexhaust gas G_(11B) having flowed through the branch exhaust gas lineL_(11B) is increased with respect to the combustion exhaust gas G_(11A)having flowed through the main exhaust gas line L_(11A). This canincrease the ratio of the combustion exhaust gas G_(11B) relative to thecombustion exhaust gas G_(11A), where the temperature of the combustionexhaust gas G_(11A) is decreased because the heat thereof has beenrecovered by the waste heat recovery boiler 11 and the temperature ofthe combustion exhaust gas G_(11B) is high because the heat thereof hasnot been recovered by the waste heat recovery boiler 11, and therefore,the temperature of the integrated combustion exhaust gas G₂₁ measured bythe first exhaust gas measurement unit 16 increases. The control unit 18may maintain the opening amounts of the flow rate control valves V_(11A)and V_(11B) to increase the feed amount of the fuel F supplied to thepower generation facility 10 so as to increase the temperature of theintegrated combustion exhaust gas G₂₁.

In a case where the temperature of the integrated combustion exhaust gasG₂₁ measured by the first exhaust gas measurement unit 16 exceeds 400°C., the control unit 18 controls at least one of the opening amount ofthe flow rate control valve V_(11A) to be increased and the openingamount of the flow rate control valve V_(11B) to be decreased, so thatthe ratio, in the integrated combustion exhaust gas G₂₁, of thecombustion exhaust gas G_(11B) flowing through the branch exhaust gasline L_(11B) is decreased with respect to the combustion exhaust gasG_(11A) flowing through the main exhaust gas line L_(11A). This candecrease the ratio of the combustion exhaust gas G_(11B) relative to thecombustion exhaust gas G_(11A), where the temperature of the combustionexhaust gas G_(11A) is decreased because the heat thereof has beenrecovered by the waste heat recovery boiler 11, and where thetemperature of the combustion exhaust gas G_(11B) is high because theheat thereof has not been recovered by the waste heat recovery boiler11, and therefore, the temperature of the integrated combustion exhaustgas G₂₁ measured by the first exhaust gas measurement unit 16 decreases.The control unit 18 may maintain the opening amounts of the flow ratecontrol valves V_(11A) and V_(11B) to decrease the feed amount of thefuel F supplied to the power generation facility 10 so as to decreasethe temperature of the integrated combustion exhaust gas G₂₁.

The control unit 18 adjusts the supply amount of the reducing agentsupplied from the reducing agent supply unit 121, and controls thenitrogen oxide concentration in the integrated combustion exhaust gasG₂₁ measured by the second exhaust gas measurement unit 17 to be apredetermined value or less. In case that the nitrogen oxideconcentration in the integrated combustion exhaust gas G₂₁ measured bythe second exhaust gas measurement unit 17 exceeds the predeterminedvalue, the control unit 18 increases the supply amount of the reducingagent from the reducing agent supply unit 121. In case that the nitrogenoxide concentration in the integrated combustion exhaust gas G₂₁measured by the second exhaust gas measurement unit 17 is less than thepredetermined value, the control unit 18 maintains or decreases thesupply amount of the reducing agent from the reducing agent supply unit121. By such control, the exhaust gas treatment device 1 can control thenitrogen oxide concentration in the integrated combustion exhaust gasG₂₁ introduced into the CO₂ recovery unit 13 to be the predeterminedvalue or less, so that it is possible to efficiently reduce the nitrogenoxide in the integrated combustion exhaust gas G₂₁ after CO₂ dischargedfrom the CO₂ recovery unit 13 is recovered.

Next, the overall operation of the exhaust gas treatment device 1according to the present embodiment will be described. The combustionexhaust gas G₁₁ discharged from the power generation facility 10 via theexhaust gas line L₁₁ is branched into the combustion exhaust gas G_(11A)flowing through the main exhaust gas line L_(11A) and the combustionexhaust gas G_(11B) flowing through the branch exhaust gas line L_(11B).The combustion exhaust gas G_(11A) flowing through the main exhaust gasline L_(11A), with the waste heat of the gas G_(11A) being recovered bythe waste heat recovery boiler 11 to decrease the temperature, after apart of the gas G_(11A) is discharged from the stack 15, is integratedin the exhaust gas line L₁₁ with the combustion exhaust gas G_(11B)flowing through the branch exhaust gas line L_(11B). The combustionexhaust gas G_(11B) flowing through the branch exhaust gas line L_(11B),in a state of a high temperature without via the waste heat recoveryboiler 11, is integrated in the exhaust gas line L_(H) with thecombustion exhaust gas G_(11A) flowing through the main exhaust gasline.

The integrated combustion exhaust gas G₂₁ in which the combustionexhaust gas G_(11A) and the combustion exhaust gas G_(11B) areintegrated is supplied via the exhaust gas line L₁₁ to the integratedwaste heat recovery boiler 12. Here, the control unit 18 controls valveopening amounts of the flow rate control valves V_(11A) and V_(11B) andthe supply amount of the fuel F supplied to the power generationfacility 10 as needed, such that the temperature of the integratedcombustion exhaust gas G₂₁ is a predetermined temperature (for example,300° C. or higher and 400° C. or lower). The integrated combustionexhaust gas G₂₁ supplied to the integrated waste heat recovery boiler 12is supplied with the reducing agent by the reducing agent supply unit121 in the nitrogen oxide removal unit 120, and, after nitrogen oxide isdecomposed and removed by selective catalytic reduction unit 122, issupplied to the CO₂ recovery unit 13. Here, the control unit 18 controlsan amount of the reducing agent supplied from the reducing agent supplyunit 121 to the integrated combustion exhaust gas G₂₁ as needed, suchthat nitrogen oxide in the integrated combustion exhaust gas G₂₁supplied to the CO₂ recovery unit 13 is a predetermined value or less.The integrated combustion exhaust gas G₂₁ supplied to the CO₂ recoveryunit 13, after CO₂ is recovered by the CO₂ absorbing liquid, isdischarged out of the exhaust gas treatment device 1. CO₂ in theintegrated combustion exhaust gas G₂₁ recovered by the CO₂ absorbingliquid is heated to be released from the CO₂ absorbing liquid, andthereafter, supplied to the CO₂ compression portion 14, and compressedand discharged.

As described above, according to the above-described embodiment, thecombustion exhaust gas G₁₁ discharged from the power generation facility10 is branched into the main exhaust gas line L_(11A) and the branchexhaust gas line L_(11B), and thereafter, the waste heat of thecombustion exhaust gas G_(11A) is recovered by the waste heat recoveryboiler 11 provided to the main exhaust gas line L_(11A), while thecombustion exhaust gas G_(11A) after the waste heat is recovered isintegrated with the combustion exhaust gas G_(11B) flowing through thebranch exhaust gas line L_(11B) in a state of high temperature that thetemperature is higher than the combustion exhaust gas G_(11A), to be theintegrated combustion exhaust gas G₂₁. This can adjust the temperatureof the integrated combustion exhaust gas G₂₁ introduced into theintegrated waste heat recovery boiler 12 to a range suitable fordecomposing and removing nitrogen oxide, such that nitrogen oxide in thecombustion exhaust gas discharged from the power generation facility 10can be efficiently removed. Since the temperature of the integratedcombustion exhaust gas G₂₁ can be adjusted to be in a range suitable fordecomposing and removing nitrogen oxide by simply providing the branchexhaust gas line L_(11B), the increase in the facility cost can be alsoreduced. Therefore, the exhaust gas treatment device 1 can be achievedin which nitrogen oxide can be efficiently removed and the increase inthe facility cost can be reduced.

The embodiment described above describes the configuration in which thewaste heat recovery boiler 11 is provided to the main exhaust gas lineL_(11A), but the waste heat recovery boiler 11 may be configured to beprovided to the branch exhaust gas line L_(11B), or the waste heatrecovery boiler 11 may be configured to be provided to both the mainexhaust gas line L_(11A) and the branch exhaust gas line L_(11B). In acase where waste heat recovery boiler 11 is provided to both the mainexhaust gas line L_(11A) and the branch exhaust gas line L_(11B), theintegrated combustion exhaust gas G₂₁ can be adjusted to a desiredtemperature by differentiating a recovery amount of the waste heat fromthe combustion exhaust gas G_(11A) in the waste heat recovery boiler 11on the main exhaust gas line L_(11A) from a recovery amount of the wasteheat from the combustion exhaust gas G_(11B) in the waste heat recoveryboiler 11 on the branch exhaust gas line L_(11B). The power generationfacility 10 may be an existing power generation facility, or a newlybuilt power generation facility. In a case where the power generationfacility 10 is an existing power generation facility, the configurationof the exhaust gas treatment device 1 according to the above-describedembodiment can be obtained by simply providing the branch exhaust gasline L_(11B) to an existing exhaust gas line.

The configuration of the integrated waste heat recovery boiler 12 in theembodiment described above can be adequately modified. FIG. 3 is aschematic view illustrating another example of the exhaust gas treatmentdevice 1 according to the above-described embodiment. In an exhaust gastreatment device 2 illustrated in FIG. 3, the integrated waste heatrecovery boiler 12 includes a steam generation unit 123 provided on adownstream stage of the nitrogen oxide removal unit 120. The steamgeneration unit 123 includes a turbine-driving steam generation unit123A provided on a downstream stage of the nitrogen oxide removal unit120 in the flow direction of the integrated combustion exhaust gas G₂₁,and a CO₂ compression portion-driving steam generation unit 123Bprovided on a downstream stage of the turbine-driving steam generationunit 123A.

The turbine-driving steam generation unit 123A recovers the waste heatof the integrated combustion exhaust gas G₂₁ from which nitrogen oxidehas been removed to generate a turbine-driving steam S₁ that is alow-pressure steam for driving the low-pressure steam turbine 19. Theturbine-driving steam generation unit 123A supplies the generatedturbine-driving steam S₁ to the low-pressure steam turbine 19 via asteam supply line L₁₂. The low-pressure steam turbine 19 may be aturbine provided outside the exhaust gas treatment device 2, or thelow-pressure steam turbine 221 in the power generation facility 10illustrated in FIG. 2. The low-pressure steam turbine 19 is rotationallydriven by the turbine-driving steam S₁ to generate power by a generator(not illustrated in the drawing). This allows the exhaust gas treatmentdevice 2 to generate power by using the waste heat of the integratedcombustion exhaust gas G₂₁ recovered by the integrated waste heatrecovery boiler 12, and therefore, the steam required for driving thelow-pressure steam turbine 19 can be reduced. The low-pressure steamturbine 19 supplies the turbine-driving steam S₁ after driving theturbine as a CO₂ absorbing liquid-regenerating steam S₂ to the CO₂recovery unit 13 via a steam discharge line L₁₃.

The CO₂ compression portion-driving steam generation unit 123B recoversthe waste heat of the integrated combustion exhaust gas G₂₁ from whichnitrogen oxide has been removed to generate a CO₂ compressionportion-driving steam S₃ that is a low-pressure steam for driving theCO₂ compression portion 14. The CO₂ compression portion-driving steamgeneration unit 123B supplies the generated CO₂ compressionportion-driving steam S₃ to the CO₂ compression portion 14 via a steamsupply line L₁₄. The CO₂ compression portion 14 drives the CO₂compression portion by using the CO₂ compression portion-driving steamS₃ to compress CO₂. This allows the exhaust gas treatment device 2 tocompress CO₂ by using the waste heat of the integrated combustionexhaust gas G₂₁ recovered by the integrated waste heat recovery boiler12, and therefore, the steam required for compressing CO₂ can bereduced. The CO₂ compression portion 14 supplies the CO₂ compressionportion-driving steam S₃ after driving the CO₂ compression portion as aCO₂ absorbing liquid-regenerating steam S₄ to the CO₂ recovery unit 13via a steam discharge line L₁₅.

The CO₂ recovery unit 13 supplies the CO₂ absorbing liquid-regeneratingsteams S₂ and S₄ to a reboiler in the CO₂ regeneration tower to releaseCO₂ from the CO₂ absorbing liquid having recovered CO₂. This allows theexhaust gas treatment device 2 to reduce the steam used for the reboilerin the CO₂ absorbing tower. The CO₂ recovery unit 13 supplies acondensed water W in which condensed is the CO₂ absorbingliquid-regenerating steams S₂ and S₄ having been used for the reboilerin the CO₂ absorbing tower to the turbine-driving steam generation unit123A and the CO₂ compression portion-driving steam generation unit 123Bin the integrated waste heat recovery boiler 12.

The control unit 18 controls a supply amount of the fuel F supplied tothe combustor 212 in the power generation facility 10, a supply amountof the turbine-driving steam S₁ supplied to the low-pressure steamturbine 19, and a supply amount of the CO₂ compression portion-drivingsteam S₃ supplied to the CO₂ compression portion 14, based on thetemperature and gas flow rate of the integrated combustion exhaust gasG₂₁, measured by the first exhaust gas measurement unit 16 andintroduced into the nitrogen oxide removal unit 120. In a case where thetemperature and gas flow rate of the integrated combustion exhaust gasG₂₁ introduced into the nitrogen oxide removal unit 120 is less than apredetermined range, the control unit 18 increases the fuel F suppliedto the combustor 212 in the power generation facility 10. In a casewhere the temperature and gas flow rate of the integrated combustionexhaust gas G₂₁ introduced into the nitrogen oxide removal unit 120exceeds the predetermined range, the control unit 18 decreases the fuelF supplied to the combustor 212 in the power generation facility 10. Ina case where the temperature and gas flow rate of the integratedcombustion exhaust gas G₂₁ introduced into the nitrogen oxide removalunit 120 is less than the predetermined range, the control unit 18decreases an opening amount of at least one of a flow rate control valveV₁₂ provided to the steam supply line L₁₂ and a flow rate control valveV₁₄ provided to the steam supply line L₁₄ to decrease the supply amountof at least one of the turbine-driving steam S₁ supplied to thelow-pressure steam turbine 19 and the CO₂ compression portion-drivingsteam S₃ supplied to the CO₂ compression portion 14. In a case where thetemperature and gas flow rate of the integrated combustion exhaust gasG₂₁ introduced into the nitrogen oxide removal unit 120 exceeds thepredetermined range, the control unit 18 increases the opening amount ofat least one of the flow rate control valve V₁₂ provided to the steamsupply line L₁₂ and the flow rate control valve V₁₄ provided to thesteam supply line L₁₄ to increase the supply amount of at least one ofthe turbine-driving steam S₁ supplied to the low-pressure steam turbine19 and the CO₂ compression portion-driving steam S₃ supplied to the CO₂compression portion 14. By such control, the temperature of theintegrated combustion exhaust gas G₂₁ introduced into the nitrogen oxideremoval unit 120 can be controlled to be in a range suitable fordecomposing and removing nitrogen oxide, so that nitrogen oxide in theintegrated combustion exhaust gas G₂₁ can be efficiently reduced.

As described above, according to the exhaust gas treatment device 2 inthe above-described embodiment, by virtue of the turbine-driving steamgeneration unit 123A and the CO₂ compression portion-driving steamgeneration unit 123B in the integrated waste heat recovery boiler 12,the turbine-driving steam S₁ required for rotationally driving thelow-pressure steam turbine 19, the CO₂ compression portion-driving steamS₃ required for compressing CO₂, and the CO₂ absorbingliquid-regenerating steams S₂ and S₄ required for regenerating the CO₂absorbing liquid can be acquired, so that an amount of the steam used inthe whole exhaust gas treatment device 2 can be reduced.

FIG. 4 is a schematic view illustrating another example of the exhaustgas treatment device 2 according to the above-described embodiment. Inan exhaust gas treatment device 3 illustrated in FIG. 4, the integratedwaste heat recovery boiler 12 includes, besides the steam generationunit 123 illustrated in FIG. 3, a heating unit 124 provided on a frontstage of the nitrogen oxide removal unit 120 where is an introducingpart of the integrated combustion exhaust gas G₂₁, and a steamgeneration unit 125 provided between the heating unit 124 and thenitrogen oxide removal unit 120. The steam generation unit 125 isprovided on a downstream stage of the heating unit 124, and includes aturbine-driving steam generation unit 125A that generates ahigh-pressure steam for rotationally driving a high-pressure steamturbine 20A of a medium-pressure/high-pressure steam turbine 20, and aturbine-driving steam generation unit 125B that is provided on adownstream stage of the turbine-driving steam generation unit 125A andgenerates a medium-pressure steam for rotationally driving amid-pressure steam turbine 20B of the medium-pressure/high-pressuresteam turbine 20.

The heating unit 124 heats the integrated combustion exhaust gas G₂₁introduced into the integrated waste heat recovery boiler 12 (forexample, 500° C. or higher and 600° C. or lower), and supplies theheated integrated combustion exhaust gas G₂₁ to the turbine-drivingsteam generation unit 125A in the steam generation unit 125. Theintegrated combustion exhaust gas G₂₁ can be heated by use of a publiclyknown general heating device. In a case where the temperature of theintegrated combustion exhaust gas G₂₁ introduced into the integratedwaste heat recovery boiler 12 is high, the heating unit 124 may not benecessarily provided.

The turbine-driving steam generation unit 125A recovers the waste heatof the integrated combustion exhaust gas G₂₁ heated by the heating unit124 to generate a turbine-driving steam S₅ that is a high-pressure steamfor driving the high-pressure steam turbine 20A of themedium-pressure/high-pressure steam turbine 20. The turbine-drivingsteam generation unit 125A supplies the generated turbine-driving steamS₅ to the high-pressure steam turbine 20A via a steam supply line L₁₆.The medium-pressure/high-pressure steam turbine 20 may be that providedoutside the exhaust gas treatment device 3, or themedium-pressure/high-pressure steam turbine 222 in the power generationfacility 10 illustrated in FIG. 2. The high-pressure steam turbine 20Ais rotationally driven by the turbine-driving steam S₅ to generate powerby a generator (not illustrated in the drawing). This allows the exhaustgas treatment device 3 to generate power by using the waste heat of theintegrated combustion exhaust gas G₂₁ recovered by the integrated wasteheat recovery boiler 12, and therefore, the steam required for drivingthe medium-pressure/high-pressure steam turbine 20 can be reduced. Thehigh-pressure steam turbine 20A supplies a turbine-driving steam S₆after driving the turbine to the turbine-driving steam generation unit125A via a steam discharge line L₁₇.

The turbine-driving steam generation unit 125B recovers the waste heatof the integrated combustion exhaust gas G₂₁ heated by the heating unit124 to generate a turbine-driving steam S₇ that is a medium-pressuresteam for driving the mid-pressure steam turbine 20B of themedium-pressure/high-pressure steam turbine 20. The turbine-drivingsteam generation unit 125B supplies the generated turbine-driving steamS₇ to the mid-pressure steam turbine 20B via a steam supply line Lis.The mid-pressure steam turbine 20B is rotationally driven by theturbine-driving steam S₇ to generate power by a generator (notillustrated in the drawing). This allows the exhaust gas treatmentdevice 3 to generate power by using the waste heat of the integratedcombustion exhaust gas G₂₁ recovered by the integrated waste heatrecovery boiler 12, and therefore, the steam required for driving themid-pressure steam turbine 20B can be reduced. The mid-pressure steamturbine 20B supplies a turbine-driving steam S₈ after driving theturbine to the turbine-driving steam generation unit 125B via a steamdischarge line L₁₉.

The control unit 18 controls supply amounts of the turbine-drivingsteams S₅ and S₇ supplied to the medium-pressure/high-pressure steamturbine 20, based on the temperature and gas flow rate of the integratedcombustion exhaust gas G₂₁, measured by the first exhaust gasmeasurement unit 16 and introduced into the nitrogen oxide removal unit120. In a case where the temperature and gas flow rate of the integratedcombustion exhaust gas G₂₁ introduced into the nitrogen oxide removalunit 120 is less than a predetermined range, the control unit 18decreases an opening amount of at least one of a flow rate control valveV₁₆ provided to the steam supply line Lib and a flow rate control valveV₁₈ provided to the steam supply line Lis to decrease at least one ofthe turbine-driving steams S₅ and S₇ supplied to themedium-pressure/high-pressure steam turbine 20. In a case where thetemperature and gas flow rate of the integrated combustion exhaust gasG₂₁ introduced into the nitrogen oxide removal unit 120 exceeds apredetermined range, the control unit 18 increases the opening amount ofat least one of the flow rate control valve V₁₆ provided to the steamsupply line L₁₆ and the flow rate control valve V₁₈ provided to thesteam supply line L₁₈ to increase at least one of the supply amounts ofthe turbine-driving steams S₅ and S₇ supplied to themedium-pressure/high-pressure steam turbine 20. By such control, thetemperature of the integrated combustion exhaust gas G₂₁ introduced intothe nitrogen oxide removal unit 120 can be controlled to be in a rangesuitable for decomposing and removing nitrogen oxide, so that nitrogenoxide in the integrated combustion exhaust gas G₂₁ can be efficientlyreduced.

As described above, according to the exhaust gas treatment device 3 inthe above-described embodiment, by virtue of the turbine-driving steamgeneration units 125A and 125B in the integrated waste heat recoveryboiler 12, the turbine-driving steams S₅ and S₇ required forrotationally driving the medium-pressure/high-pressure steam turbine 20can be acquired, so that an amount of the steam used in the wholeexhaust gas treatment device 3 can be reduced.

Second Embodiment

Next, a second embodiment of the present invention will be described. Inthe following embodiment, a description is mainly given of differencesfrom the embodiment described above to omit duplicated explanations.Note that, components the same as those in the first embodimentdescribed above are designated by the same reference signs. Furthermore,embodiments described below can be suitably combined for implementation.

FIG. 5 is a schematic view illustrating an example of an exhaust gastreatment device 4 according to the second embodiment of the presentinvention. As illustrated in FIG. 5, the exhaust gas treatment device 4according to the present embodiment recovers waste heat of combustionexhaust gases G₁₁₋₁ and G₁₁₋₂ respectively discharged from two powergeneration facilities 10-1 and 10-2 by the integrated waste heatrecovery boiler 12, and thereafter, recovers CO₂ contained in thecombustion exhaust gases G₁₁₋₁ and G₁₁₋₂ by the CO₂ recovery unit 13.The exhaust gas treatment device 4 includes the power generationfacility (first power generation facility) 10-1 discharging thecombustion exhaust gas (first combustion exhaust gas) G₁₁₋₁, the powergeneration facility (second power generation facility) 10-2 dischargingthe combustion exhaust gas (second combustion exhaust gas) G₁₁₋₂, awaste heat recovery boiler 11-1 provided on a downstream stage of thepower generation facility 10-1 in a flow direction of the combustionexhaust gas G₁₁₋₁, the integrated waste heat recovery boiler 12 providedon a downstream stage of the waste heat recovery boiler 11-1, the CO₂recovery unit 13 provided on a downstream stage of the integrated wasteheat recovery boiler 12, and the CO₂ compression portion 14 provided ona downstream stage of the CO₂ recovery unit 13. A stack 15-1 discharginga part of the combustion exhaust gas G₁₁₋₁ is provided between the wasteheat recovery boiler 11-1 and the integrated waste heat recovery boiler12.

The power generation facility 10-1 discharges the combustion exhaust gasG₁₁₋₁ generated by the power generation to an exhaust gas line (firstexhaust gas flow path) L₁₁₋₁. The exhaust gas line L₁₁₋₁ is providedwith the waste heat recovery boiler 11-1, the stack 15-1, and a flowrate control valve V₁₁₋₁ in this order. The flow rate control valveV₁₁₋₁ adjusts a flow rate of the combustion exhaust gas G₁₁₋₁ flowingthrough the exhaust gas line L₁₁₋₁. The waste heat recovery boiler 11-1recovers the waste heat of the combustion exhaust gas G₁₁₋₁ that isdischarged from the power generation facility 10-1 and flows through theexhaust gas line L₁₁₋₁, and supplies the combustion exhaust gas G₁₁₋₁from which the waste heat has been recovered to the stack 15-1. Thestack 15-1 discharges a part of the combustion exhaust gas G₁₁₋₁ tooutside as needed, and supplies the combustion exhaust gas G₁₁₋₁ to theintegrated waste heat recovery boiler 12.

The power generation facility 10-2 discharges the combustion exhaust gasG₁₁₋₂ generated by the power generation to an exhaust gas line (secondexhaust gas flow path) L₁₁₋₂. The exhaust gas line L₁₁₋₂ is providedwith a flow rate control valve V₁₁₋₂. The flow rate control valve V₁₁₋₂adjusts a flow rate of the combustion exhaust gas G₁₁₋₂ flowing throughthe exhaust gas line L₁₁₋₂.

The integrated waste heat recovery boiler 12 is supplied with theintegrated combustion exhaust gas G₂₁ in which the combustion exhaustgas G₁₁₋₁ flowing through the exhaust gas line L₁₁₋₁ and the combustionexhaust gas G₁₁₋₂ flowing through the exhaust gas line L₁₁₋₂ areintegrated. The integrated waste heat recovery boiler 12 is providedwith the nitrogen oxide removal unit 120 that reduces and removesnitrogen oxide such as nitrogen monoxide and nitrogen dioxide containedin the integrated combustion exhaust gas G₂₁.

The exhaust gas treatment device 4 includes the control unit 18 thatcontrols opening amounts of the flow rate control valve V₁₁₋₁ and flowrate control valve V₁₁₋₂, and the supply amount of the fuel supplied tothe power generation facility 10, based on the gas flow rate andtemperature of the integrated combustion exhaust gas G₂₁ measured by thefirst exhaust gas measurement unit 16. The control unit 18 adjusts theopening amounts of the flow rate control valve V₁₁₋₁ and flow ratecontrol valve V₁₁₋₂, and the supply amounts of the fuels F supplied tothe power generation facilities 10-1 and 10-2 to control such that thetemperature of the integrated combustion exhaust gas G₂₁ measured by thefirst exhaust gas measurement unit 16 is 300° C. or higher and 400° C.or lower. By such control, the exhaust gas treatment device 4 can makethe temperature of the integrated combustion exhaust gas G₂₁ supplied tothe nitrogen oxide removal unit 120 in the integrated waste heatrecovery boiler 12 a temperature suitable for decomposing and removingnitrogen oxide, so that nitrogen oxide in the integrated combustionexhaust gas G₂₁ can be further more efficiently decomposed and removed.

In a case where the temperature of the integrated combustion exhaust gasG₂₁ measured by the first exhaust gas measurement unit 16 is lower than300° C., the control unit 18 controls at least one of the opening amountof the flow rate control valve V₁₁₋₁ to be decreased and the openingamount of the flow rate control valve V₁₁₋₂ to be increased, so that aratio, in the integrated combustion exhaust gas G₂₁, of the combustionexhaust gas G₁₁₋₂ flowing through the exhaust gas line L₁₁₋₂ isincreased with respect to the combustion exhaust gas G₁₁₋₁ flowingthrough the exhaust gas line L₁₁₋₁. This can increase the ratio of thecombustion exhaust gas G₁₁₋₂ relative to the combustion exhaust gasG₁₁₋₁, where the temperature of the combustion exhaust gas G₁₁₋₁ isdecreased because the heat thereof has been recovered by the waste heatrecovery boiler 11-1, and where the temperature of the combustionexhaust gas G₁₁₋₂ is high because the heat thereof has not beenrecovered by the waste heat recovery boiler 11-1, and therefore, thetemperature of the integrated combustion exhaust gas G₂₁ measured by thefirst exhaust gas measurement unit 16 increases. The control unit 18 maymaintain the opening amounts of the flow rate control valve V₁₁₋₁ andflow rate control valve V₁₁₋₂ to increase the supply amount of the fuelsupplied to the power generation facility 10 so as to increase thetemperature of the integrated combustion exhaust gas G₂₁.

In a case where the temperature of the integrated combustion exhaust gasG₂₁ measured by the first exhaust gas measurement unit 16 exceeds 400°C., the control unit 18 controls at least one of the opening amount ofthe flow rate control valve V₁₁₋₁ to be increased and the opening amountof the flow rate control valve V₁₁₋₂ to be decreased, so that the ratio,in the integrated combustion exhaust gas G₂₁, of the combustion exhaustgas G₁₁₋₂ flowing through the exhaust gas line L₁₁₋₂ is decreased withrespect to the combustion exhaust gas G₁₁₋₁ flowing through the exhaustgas line L₁₁₋₁. This can decrease the ratio of the combustion exhaustgas G₁₁₋₂ relative to the combustion exhaust gas G₁₁₋₁, where thetemperature of the combustion exhaust gas G₁₁₋₁ is decreased because theheat thereof has been recovered by the waste heat recovery boiler 11-1,and where the temperature of the combustion exhaust gas G₁₁₋₂ is highbecause the heat thereof has not been recovered by the waste heatrecovery boiler 11-1, and therefore, the temperature of the integratedcombustion exhaust gas G₂₁ measured by the first exhaust gas measurementunit 16 decreases. The control unit 18 may maintain the opening amountsof the flow rate control valve V₁₁₋₁ and flow rate control valve V₁₁₋₂to decrease the supply amount of the fuel supplied to the powergeneration facility 10 so as to decrease the temperature of theintegrated combustion exhaust gas G₂₁. For the other components,descriptions are omitted since the other components are the same asthose of the exhaust gas treatment device 1 illustrated in FIG. 1.

Next, the overall operation of the exhaust gas treatment device 4according to the present embodiment will be described. The combustionexhaust gas G₁₁₋₁ discharged from the power generation facility 10-1,with the waste heat of the gas G₁₁₋₁ being recovered by the waste heatrecovery boiler 11-1 via the exhaust gas line L₁₁₋₁ to decrease thetemperature, after a part of the gas G₁₁₋₁ is discharged from the stack15-1, is supplied to an integrated exhaust gas line L₂₁. The combustionexhaust gas G₁₁₋₂ discharged from the power generation facility 10-2 issupplied via the exhaust gas line L₁₁₋₂ to the integrated exhaust gasline L₂₁. In the integrated exhaust gas line L₂₁, the combustion exhaustgas G₁₁₋₁ and the combustion exhaust gas G₁₁₋₂ are integrated to obtainthe integrated combustion exhaust gas G₂₁, where the waste heat of thecombustion exhaust gas G₁₁₋₁ is recovered by the waste heat recoveryboiler 11-1 to decrease the temperature thereof and the combustionexhaust gas G₁₁₋₂ has a temperature higher relative to the combustionexhaust gas G₁₁₋₁, and the resultant integrated combustion exhaust gasG₂₁ is supplied to the integrated waste heat recovery boiler 12. Here,the control unit 18 controls the opening amounts of the flow ratecontrol valves V₁₁₋₁ and V₁₁₋₂ and the supply amount of the fuel Fsupplied to the power generation facility 10 as needed, such that thetemperature of the integrated combustion exhaust gas G₂₁ is apredetermined temperature (for example, 300° C. or higher and 400° C. orlower). The integrated combustion exhaust gas G₂₁ supplied to theintegrated waste heat recovery boiler 12 is supplied with the reducingagent by the reducing agent supply unit 121 in the nitrogen oxideremoval unit 120, and, after nitrogen oxide is decomposed and removed byselective catalytic reduction unit 122, is supplied to the CO₂ recoveryunit 13. Here, the control unit 18 controls an amount of the reducingagent supplied from the reducing agent supply unit 121 to the integratedcombustion exhaust gas G₂₁ as needed, such that nitrogen oxide in theintegrated combustion exhaust gas G₂₁ supplied to the CO₂ recovery unit13 is a predetermined value or less. The integrated combustion exhaustgas G₂₁ supplied to the CO₂ recovery unit 13, after CO₂ is recovered bythe CO₂ absorbing liquid, is discharged out of the exhaust gas treatmentdevice 4. CO₂ in the integrated combustion exhaust gas G₂₁ recovered bythe CO₂ absorbing liquid is heated to be released from the CO₂ absorbingliquid, and thereafter, supplied to the CO₂ compression portion 14, andcompressed and discharged.

As described above, according to the above-described embodiment, thewaste heat of the combustion exhaust gas G₁₁₋₁ discharged from the powergeneration facility 10-1 is recovered by the waste heat recovery boiler11-1 provided to the exhaust gas line L₁₁₋₁, while the combustionexhaust gas G₁₁₋₁ after the waste heat is recovered is integrated withthe combustion exhaust gas G₁₁₋₂ discharged from the power generationfacility 10-2 and flowing through the exhaust gas line L₁₁₋₂ in a stateof high temperature that the temperature is higher than the combustionexhaust gas G₁₁₋₁, and then, the integrated combustion exhaust gas G₂₁is resulted. This can adjust the temperature of the integratedcombustion exhaust gas G₂₁ introduced into the integrated waste heatrecovery boiler 12 to a range suitable for decomposing and removingnitrogen oxide, such that nitrogen oxide in the combustion exhaust gasesG₁₁₋₁ and G₁₁₋₂ discharged from the power generation facility 10 can beefficiently removed. Since the exhaust gas line L₁₁₋₂ that is one of theexhaust gas lines L₁₁₋₁ and L₁₁₋₂ does not need to be provided with thenitrogen oxide removal unit 120, the increase in the facility cost canbe also reduced. Therefore, the exhaust gas treatment device 4 can beachieved in which nitrogen oxide can be efficiently removed and theincrease in the facility cost can be reduced.

The embodiment described above describes the configuration in which thewaste heat recovery boiler 11-1 is provided to the exhaust gas lineL₁₁₋₁, but the waste heat recovery boiler 11-1 may be configured to beprovided to the exhaust gas line L₁₁₋₂, or the waste heat recoveryboiler 11-1 may be configured to be provided to both the exhaust gasline L₁₁₋₁ and the exhaust gas line L₁₁₋₂. In a case where waste heatrecovery boiler 11-1 is provided to both the exhaust gas line L₁₁₋₁ andthe exhaust gas line L₁₁₋₂, the integrated combustion exhaust gas G₂₁can be adjusted to a desired temperature by differentiating a recoveryamount of the waste heat from the combustion exhaust gas G₁₁₋₁ in thewaste heat recovery boiler 11-1 on the exhaust gas line L₁₁₋₁ from arecovery amount of the waste heat from the combustion exhaust gas G₁₁₋₂in the waste heat recovery boiler 11 on the exhaust gas line L₁₁₋₂. Eachof two power generation facilities 10-1 and 10-2 may be an existingpower generation facility, or a newly built power generation facility.For example, in a case where the power generation facility 10-1 is anexisting power generation facility, the integrated combustion exhaustgas G₂₁ can be adjusted to a desired temperature only by newly providingthe power generation facility 10-2 and the exhaust gas line L₁₁₋₂. Theconfiguration of the integrated waste heat recovery boiler 12 may be thesame as the configuration illustrated in FIG. 3 or FIG. 4.

FIG. 6 is a schematic view illustrating another example of the exhaustgas treatment device 4 according to the second embodiment of the presentinvention. As illustrated in FIG. 6, an exhaust gas treatment device 5according to the present embodiment recovers waste heat of combustionexhaust gases G₁₁₋₁, G₁₁₋₂, G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ respectivelydischarged from five power generation facilities 10-1, 10-2, 10-3, 10-4,and 10-5 by the integrated waste heat recovery boiler 12, andthereafter, recovers CO₂ contained in the combustion exhaust gasesG₁₁₋₁, G₁₁₋₂, G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ by the CO₂ recovery unit 13. Theexhaust gas treatment device 5 includes the power generation facility(first power generation facility) 10-1 discharging the combustionexhaust gas (first combustion exhaust gas) G₁₁₋₁, the power generationfacility (first power generation facility) 10-2 discharging thecombustion exhaust gas (first combustion exhaust gas) G₁₁₋₂, the powergeneration facility (second power generation facility) 10-3 dischargingthe combustion exhaust gas (second combustion exhaust gas) G₁₁₋₃, thepower generation facility (second power generation facility) 10-4discharging the combustion exhaust gas (second combustion exhaust gas)G₁₁₋₄, the power generation facility (second power generation facility)10-5 discharging the combustion exhaust gas (second combustion exhaustgas) G₁₁₋₅, the waste heat recovery boiler 11-1 provided on a downstreamstage of the power generation facility 10-1 in a flow direction of thecombustion exhaust gas G₁₁₋₁, a waste heat recovery boiler 11-2 providedon a downstream stage of the power generation facility 10-2 in a flowdirection of the combustion exhaust gas G₁₁₋₂, the integrated waste heatrecovery boiler 12 provided on a downstream stage of the waste heatrecovery boiler 11-1, the CO₂ recovery unit 13 provided on a downstreamstage of the integrated waste heat recovery boiler 12, and the CO₂compression portion 14 provided on a downstream stage of the CO₂recovery unit 13. The stack 15-1 discharging a part of the combustionexhaust gas G₁₁₋₁ is provided between the waste heat recovery boiler11-1 and the integrated waste heat recovery boiler 12, and a stack 15-2discharging a part of the combustion exhaust gas G₁₁₋₂ is providedbetween the waste heat recovery boiler 11-2 and the integrated wasteheat recovery boiler 12.

The power generation facilities 10-1 and 10-2 discharge the combustionexhaust gases G₁₁₋₁ and G₁₁₋₂ generated by the power generation to theexhaust gas lines (first exhaust gas flow path) L₁₁₋₁ and L₁₁₋₂.

The exhaust gas lines L₁₁₋₁ and L₁₁₋₂ are provided with respectively thewaste heat recovery boilers 11-1 and 11-2, the stacks 15-1 and 15-2, andthe flow rate control valves V₁₁₋₁ and V₁₁₋₂ in this order. The flowrate control valves V₁₁₋₁ and V₁₁₋₂ adjust flow rates of the combustionexhaust gases G₁₁₋₁ and G₁₁₋₂ flowing through the exhaust gases linesL₁₁₋₁ and L₁₁₋₂, respectively. The waste heat recovery boilers 11-1 and11-2 recover the waste heat of the combustion exhaust gases G₁₁₋₁ andG₁₁₋₂ that are discharged from the power generation facilities 10-1 and10-2 and flow through the exhaust gas lines L₁₁₋₁ and L₁₁₋₂, and supplythe combustion exhaust gases G₁₁₋₁ and G₁₁₋₂ from which the waste heathas been recovered to the stacks 15-1 and 15-2, respectively. The stacks15-1 and 15-2 supply the combustion exhaust gases G₁₁₋₁ and G₁₁₋₂ to theintegrated waste heat recovery boiler 12, and discharge a part of thecombustion exhaust gases G₁₁₋₁ and G₁₁₋₂ to outside as needed.

The power generation facilities 10-3, 10-4, and 10-5 discharge thecombustion exhaust gases G₁₁₋₃, G₁₁₋₄ and G₁₁₋₅ generated by the powergeneration to the exhaust gas lines (second exhaust gas flow path)L₁₁₋₃, L₁₁₋₄ and L₁₁₋₅, respectively. The exhaust gas lines L₁₁₋₃, L₁₁₋₄and L₁₁₋₅ are provided with flow rate control valves V₁₁₋₃, V₁₁₋₄, andV₁₁₋₅, respectively.

The flow rate control valves V₁₁₋₃, V₁₁₋₄, and V₁₁₋₅ adjust flow ratesof the combustion exhaust gases G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ flowing throughthe exhaust gases lines L₁₁₋₃, L₁₁₋₄ and L₁₁₋₅, respectively.

The integrated waste heat recovery boiler 12 is supplied with theintegrated combustion exhaust gas G₂₁ in which the combustion exhaustgases G₁₁₋₁, G₁₁₋₂, G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ flowing through the exhaustgas lines L₁₁₋₁, L₁₁₋₂, L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅ are integrated. Theintegrated waste heat recovery boiler 12 is provided with, withinthereof, the nitrogen oxide removal unit 120 that reduces and removesnitrogen oxide such as nitrogen monoxide and nitrogen dioxide containedin the integrated combustion exhaust gas G₂₁.

The exhaust gas treatment device 5 includes the control unit 18 thatcontrols opening amounts of the flow rate control valves V₁₁₋₁, V₁₁₋₂,V₁₁₋₃, V₁₁₋₄, and V₁₁₋₅ and supply amounts of the fuels F supplied tothe power generation facilities 10-1, 10-2, 10-3, 10-4, and 10-5, basedon the gas flow rate and temperature of the integrated combustionexhaust gas G₂₁ measured by the first exhaust gas measurement unit 16.The control unit 18 adjusts respectively the opening amounts of the flowrate control valves V₁₁₋₁, V₁₁₋₂, V₁₁₋₃, V₁₁₋₄, and V₁₁₋₅, and thesupply amounts of the fuels F supplied to the power generationfacilities 10-1, 10-2, 10-3, 10-4, and 10-5 to control such that thetemperature of the integrated combustion exhaust gas G₂₁ measured by thefirst exhaust gas measurement unit 16 is 300° C. or higher and 400° C.or lower. By such control, the exhaust gas treatment device 5 can makethe temperature of the integrated combustion exhaust gas G₂₁ supplied tothe nitrogen oxide removal unit 120 in the integrated waste heatrecovery boiler 12 a temperature suitable for decomposing and removingnitrogen oxide, so that nitrogen oxide in the integrated combustionexhaust gas G₂₁ can be further more efficiently decomposed and removed.

In a case where the temperature of the integrated combustion exhaust gasG₂₁ measured by the first exhaust gas measurement unit 16 is lower than300° C., the control unit 18 controls at least one of the openingamounts of the flow rate control valves V₁₁₋₁ and V₁₁₋₂ to be decreasedand the opening amounts of the flow rate control valves V₁₁₋₃, V₁₁₋₄,and V₁₁₋₅ to be increased, so that a ratio, in the integrated combustionexhaust gas G₂₁, of the combustion exhaust gases G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅flowing through the exhaust gas lines L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅ isincreased with respect to the combustion exhaust gases G₁₁₋₁ and G₁₁₋₂flowing through the exhaust gas lines L₁₁₋₁ and L₁₁₋₂. This can increasethe ratio of the combustion exhaust gases G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅relative to the combustion exhaust gases G₁₁₋₁ and G₁₁₋₂, where thetemperatures of the combustion exhaust gases G₁₁₋₁ and G₁₁₋₂ aredecreased because the heats thereof have been recovered by the wasteheat recovery boilers 11-1 and 11-2, and where the temperatures of thecombustion exhaust gases G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ are high because theheats thereof have not been recovered by the waste heat recovery boilers11-1 and 11-2, and therefore, the temperature of the integratedcombustion exhaust gas G₂₁ measured by the first exhaust gas measurementunit 16 increases. The control unit 18 may maintain the opening amountsof the flow rate control valves V₁₁₋₁, V₁₁₋₂, V₁₁₋₃, V₁₁₋₄, and V₁₁₋₅ toincrease the supply amounts of the fuels F supplied to the powergeneration facilities 10-1, 10-2, 10-3, 10-4, and 10-5 so as to increasethe temperature of the integrated combustion exhaust gas G₂₁.

In a case where the temperature of the integrated combustion exhaust gasG₂₁ measured by the first exhaust gas measurement unit 16 exceeds 400°C., the control unit 18 controls at least one of the opening amounts ofthe flow rate control valves V₁₁₋₁ and V₁₁₋₂ to be increased and theopening amounts of the flow rate control valves V₁₁₋₃, V₁₁₋₄, and V₁₁₋₅to be decreased, so that the ratio, in the integrated combustion exhaustgas G₂₁, of the combustion exhaust gases G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ flowingthrough the exhaust gas lines L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅ is decreased withrespect to the combustion exhaust gas G₁₁₋₁ and G₁₁₋₂ flowing throughthe exhaust gas lines L₁₁₋₁ and L₁₁₋₂. This can decrease the ratio ofthe combustion exhaust gases G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ relative to thecombustion exhaust gases G₁₁₋₁ and G₁₁₋₂, where the temperatures of thecombustion exhaust gases G₁₁₋₁ and G₁₁₋₂ are decreased because the heatsthereof have been recovered by the waste heat recovery boilers 11-1 and11-2, and where the temperatures of the combustion exhaust gases G₁₁₋₃,G₁₁₋₄, and G₁₁₋₅ are high because the heats thereof have not beenrecovered by the waste heat recovery boilers 11-1 and 11-2, andtherefore, the temperature of the integrated combustion exhaust gas G₂₁measured by the first exhaust gas measurement unit 16 decreases. Thecontrol unit 18 may maintain the opening amounts of the flow ratecontrol valves V₁₁₋₁, V₁₁₋₂, V₁₁₋₃, V₁₁₋₄, and V₁₁₋₅ to decrease thesupply amount of the fuel supplied to the power generation facility 10so as to decrease the temperature of the integrated combustion exhaustgas G₂₁. For the other components, descriptions are omitted since theother components are the same as those of the exhaust gas treatmentdevice 1 illustrated in FIG. 1.

Next, the overall operation of the exhaust gas treatment device 5according to the present embodiment will be described. The combustionexhaust gases G₁₁₋₁ and G₁₁₋₂ discharged from the power generationfacilities 10-1 and 10-2, with the waste heat of the gases G₁₁₋₁ andG₁₁₋₂ being recovered by the waste heat recovery boilers 11-1 and 11-2via the exhaust gas lines L₁₁₋₁ and L₁₁₋₂ to decrease the temperatures,after a part of the gases G₁₁₋₁ and G₁₁₋₂ is discharged from the stacks15-1 and 15-2, are supplied to an integrated exhaust gas line L₂₁. Thecombustion exhaust gases G₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ discharged from thepower generation facilities 10-3, 10-4, and 10-5 are supplied via theexhaust gas lines L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅ to the integrated exhaust gasline L₂₁. In the integrated exhaust gas line L₂₁, the combustion exhaustgases G₁₁₋₁ and G₁₁₋₂ and the combustion exhaust gases G₁₁₋₃, G₁₁₋₄, andG₁₁₋₅ are integrated to obtain the integrated combustion exhaust gasG₂₁, where the waste heat of the combustion exhaust gases G₁₁₋₁ andG₁₁₋₂ is recovered by the waste heat recovery boilers 11-1 and 11-2 todecrease the temperatures thereof and the combustion exhaust gasesG₁₁₋₃, G₁₁₋₄, and G₁₁₋₅ have temperatures higher relative to thecombustion exhaust gases G₁₁₋₁ and G₁₁₋₂, and the resultant integratedcombustion exhaust gas G₂₁ is supplied to the integrated waste heatrecovery boiler 12. Here, the control unit 18 controls the openingamounts of the flow rate control valves V₁₁₋₁ and V₁₁₋₂ and the supplyamount of the fuel supplied to the power generation facility 10 asneeded, such that the temperature of the integrated combustion exhaustgas G₂₁ is a predetermined temperature (for example, 300° C. or higherand 400° C. or lower). The integrated combustion exhaust gas G₂₁supplied to the integrated waste heat recovery boiler 12 is suppliedwith the reducing agent by the reducing agent supply unit 121 in thenitrogen oxide removal unit 120, and, after nitrogen oxide is decomposedand removed by selective catalytic reduction unit 122, is supplied tothe CO₂ recovery unit 13. Here, the control unit 18 controls an amountof the reducing agent supplied from the reducing agent supply unit 121to the integrated combustion exhaust gas G₂₁ as needed, such thatnitrogen oxide in the integrated combustion exhaust gas G₂₁ supplied tothe CO₂ recovery unit 13 is a predetermined value or less. Theintegrated combustion exhaust gas G₂₁ supplied to the CO₂ recovery unit13, after CO₂ is recovered by the CO₂ absorbing liquid, is dischargedout of the exhaust gas treatment device 5. CO₂ in the integratedcombustion exhaust gas G₂₁ recovered by the CO₂ absorbing liquid isheated to be released from the CO₂ absorbing liquid, and thereafter,supplied to the CO₂ compression portion 14, and compressed anddischarged.

As described above, according to the above-described embodiment, thewaste heat of the combustion exhaust gases G₁₁₋₁ and G₁₁₋₂ dischargedfrom the power generation facilities 10-1 and 10-2 is recovered by thewaste heat recovery boilers 11-1 and 11-2 provided to the exhaust gaslines L₁₁₋₁ and L₁₁₋₂, while the combustion exhaust gases G₁₁₋₁ andG₁₁₋₂ after the waste heat is recovered are integrated with thecombustion exhaust gas G₁₁₋₂ discharged from the power generationfacilities 10-3, 10-4, and 10-5 and flowing through the exhaust gaslines L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅ in a state of high temperature that thetemperature is higher than the combustion exhaust gases G₁₁₋₁ and G₁₁₋₂,and then, the integrated combustion exhaust gas G₂₁ is resulted. Thiscan adjust the temperature of the integrated combustion exhaust gas G₂₁introduced into the integrated waste heat recovery boiler 12 to a rangesuitable for decomposing and removing nitrogen oxide, such that nitrogenoxide in the combustion exhaust gas discharged from the power generationfacility 10 can be efficiently removed. Since at least one exhaust gasline (three exhaust gas lines L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅ in the presentembodiment) of the exhaust gas lines L₁₁₋₁, L₁₁₋₂, L₁₁₋₃, L₁₁₋₄, andL₁₁₋₅ do not need to be provided with the nitrogen oxide removal unit120, the increase in the facility cost can be also reduced. Therefore,the exhaust gas treatment device 5 can be achieved in which nitrogenoxide can be efficiently removed and the increase in the facility costcan be reduced.

The embodiment described above describes the configuration in which thewaste heat recovery boilers 11-1 and 11-2 are provided to the exhaustgas lines L₁₁₋₁ and L₁₁₋₂, but the waste heat recovery boiler 11 may beconfigured to be provided to at least one exhaust gas line L₁₁, or thewaste heat recovery boiler 11 may be configured to be provided to all ofthe exhaust gas lines L₁₁₋₁, L₁₁₋₂, L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅. In thiscase, the integrated combustion exhaust gas G₂₁ can be adjusted to adesired temperature by differentiating recovery amounts of the wasteheat from the combustion exhaust gases G₁₁₋₁, G₁₁₋₂, G₁₁₋₃, G₁₁₋₄, andG₁₁₋₅ in the waste heat recovery boiler 11 on the exhaust gas linesL₁₁₋₁, L₁₁₋₂, L₁₁₋₃, L₁₁₋₄, and L₁₁₋₅. Each of the power generationfacilities 10-1, 10-2, 10-3, 10-4, and 10-5 may be an existing powergeneration facility, or a newly built power generation facility. Theconfiguration of the integrated waste heat recovery boiler 12 may be thesame as the configuration illustrated in FIG. 3 or FIG. 4.

EXAMPLE

The present inventors investigated in detail effects to reduce theaccumulation amount of the nitrogen oxide (NO₂)-derived component in theCO₂ absorbing liquid in the exhaust gas treatment device according tothe above-described embodiment. Hereinafter, content investigated by thepresent inventor will be described.

FIG. 7 is an explanatory diagram illustrating an accumulation amount ofa nitrogen oxide-derived component in a CO₂ absorbing liquid in theexhaust gas treatment device according to an example and a comparativeexample. FIG. 7 illustrates a comparison, in the exhaust gas treatmentdevice according to the above-described embodiment, between theaccumulation amount of the nitrogen oxide-derived component in a casewhere an exhaust gas temperature of the integrated combustion exhaustgas G₂₁ introduced into the nitrogen oxide removal unit 120 was made tobe in a range of 300° C. or higher and 400° C. or lower (refer to theworking example), and the accumulation amount of the nitrogenoxide-derived component in a case where an exhaust gas temperature ofthe combustion exhaust gas introduced into the nitrogen oxide removalunit 120 was made to be 250° C. (refer to the comparative example). Asillustrated in FIG. 7, by adjusting the exhaust gas temperature of theintegrated combustion exhaust gas G₂₁ to the range of 300° C. or greaterand 400° C. or lower, the accumulation amount of the nitrogenoxide-derived component in the CO₂ absorbing liquid can be reduced to0.2 times and a reclaiming frequency of the CO₂ absorbing liquid can bereduced to about one-fifth as compared with the case that the exhaustgas temperature the combustion exhaust gas is made to be 250° C. Fromthis result, according to the exhaust gas treatment device of theabove-described embodiment, it can be seen that the nitrogen oxideaccumulated in the CO₂ absorbing liquid can be extremely reduced, and anoperation cost of the exhaust gas treatment device can be reduced.

REFERENCE SIGNS LIST

-   1, 2, 3, 4, 5 Exhaust gas treatment device-   10, 10-1, 10-2, 10-3, 10-4, 10-5 Power generation facility-   11 Waste heat recovery boiler-   12 Integrated waste heat recovery boiler-   13 CO₂ recovery unit-   14 CO₂ compression portion-   15 Stack-   16 First exhaust gas measurement unit-   17 Second exhaust gas measurement unit-   18 Control unit-   19 Low-pressure steam turbine-   20 Mid-pressure/high-pressure steam turbine-   210 Gas turbine-   211 Compressor-   212 Combustor-   213 Turbine-   221 Low-pressure steam turbine-   222 Mid-pressure/high-pressure steam turbine-   222A Mid-pressure steam turbine-   222B High-pressure steam turbine-   230 Generator-   240 Turbine-   A Air-   F Fuel-   G₁₁, G₁₁₋₁, G₁₁₋₂, G₁₁₋₃, G₁₁₋₄, G₁₁₋₅ Combustion exhaust gas-   G₂₁ Integrated combustion exhaust gas-   L₁₁, L₁₁₋₁, L₁₁₋₂, L₁₁₋₃, L₁₁₋₄, L₁₁₋₅ Exhaust gas line-   L_(11A) Main exhaust gas line-   L_(11B) Branch exhaust gas line-   L₂₁ Integrated exhaust gas line-   V_(11A), V_(11B), V₁₁₋₁, V₁₁₋₂, V₁₁₋₃, V₁₁₋₄, V₁₁₋₅ Flow rate    control valve

1. An exhaust gas treatment device comprising: a first exhaust gas flow path through which a first combustion exhaust gas discharged from a power generation facility flows; a waste heat recovery unit provided to the first exhaust gas flow path and recovers waste heat of the first combustion exhaust gas; a second exhaust gas flow path branched from the first exhaust gas flow path and provided between a front stage and downstream stage of the waste heat recovery unit on the first exhaust gas flow path, in which at least a part of the first combustion exhaust gas flowing through the first exhaust gas flow path flows, as a second combustion exhaust gas, through the second exhaust gas flow path; a nitrogen oxide removal unit configured to remove nitrogen oxide in an integrated combustion exhaust gas into which the first combustion exhaust gas and the second combustion exhaust gas are integrated, the first combustion exhaust gas flowing through the first exhaust gas flow path with the waste heat of the first combustion exhaust gas having been recovered by the waste heat recovery unit, and the second combustion exhaust gas flowing through the second exhaust gas flow path with a temperature of the second combustion exhaust gas being higher relative to the first combustion exhaust gas; an integrated waste heat recovery unit configured to recover waste heat of the integrated combustion exhaust gas with the nitrogen oxide having been removed by the nitrogen oxide removal unit; and a CO₂ recovery unit configured to recover CO₂ in the integrated combustion exhaust gas by a CO₂ absorbing liquid with the waste heat of the integrated combustion exhaust gas having been recovered by the integrated waste heat recovery unit.
 2. The exhaust gas treatment device according to claim 1, further comprising: a control unit that adjusts a flow rate of the first combustion exhaust gas flowing through the first exhaust gas flow path and a flow rate of the second combustion exhaust gas flowing through the second exhaust gas flow path to control such that a temperature of the integrated combustion exhaust gas introduced into the nitrogen oxide removal unit is 300° C. or higher and 400° C. or lower.
 3. An exhaust gas treatment device comprising: a first exhaust gas flow path through which a first combustion exhaust gas discharged from a first power generation facility flows; a second exhaust gas flow path through which a second combustion exhaust gas discharged from a second power generation facility flows; a waste heat recovery unit provided to the first exhaust gas flow path and recovers waste heat of the first combustion exhaust gas; a nitrogen oxide removal unit configured to remove nitrogen oxide in an integrated combustion exhaust gas into which the first combustion exhaust gas and the second combustion exhaust gas are integrated, the first combustion exhaust gas flowing through the first exhaust gas flow path with the waste heat of the first combustion exhaust gas having been recovered by the waste heat recovery unit, and the second combustion exhaust gas flowing through the second exhaust gas flow path with a temperature of the second combustion exhaust gas being higher relative to the first combustion exhaust gas; an integrated waste heat recovery unit configured to recover waste heat of the integrated combustion exhaust gas with the nitrogen oxide having been removed by the nitrogen oxide removal unit; and a CO₂ recovery unit that recovers CO₂ in the integrated combustion exhaust gas by a CO₂ absorbing liquid with the waste heat of the integrated combustion exhaust gas having been recovered by the integrated waste heat recovery unit.
 4. The exhaust gas treatment device according to claim 3, further comprising: a control unit configured to adjust a flow rate of each of the combustion exhaust gases flowing through the first exhaust gas flow path and the second exhaust gas flow path to control such that a temperature of the integrated combustion exhaust gas introduced into the nitrogen oxide removal unit is 300° C. or higher and 400° C. or lower.
 5. The exhaust gas treatment device according to claim 1, wherein the nitrogen oxide removal unit is provided within the integrated waste heat recovery unit.
 6. The exhaust gas treatment device according to claim 1, wherein the nitrogen oxide removal unit includes a reducing agent injection unit configured to inject a nitrogen oxide removal catalyst removing the nitrogen oxide and a reducing agent.
 7. The exhaust gas treatment device according to claim 6, further comprising: a control unit configured to control a supply amount of the reducing agent, based on a gas flow rate and nitrogen oxide concentration of the integrated combustion exhaust gas introduced into the CO₂ recovery unit.
 8. The exhaust gas treatment device according to claim 1, wherein the integrated waste heat recovery unit generates a CO₂ compression portion-driving steam for compressing CO₂ discharged from the CO₂ recovery unit by using the waste heat of the integrated combustion exhaust gas with the nitrogen oxide having been removed, and supplies the generated CO₂ compression portion-driving steam to a CO₂ compression portion.
 9. The exhaust gas treatment device according to claim 1, wherein the integrated waste heat recovery unit generates a turbine-driving steam by using the waste heat of the integrated combustion exhaust gas with the nitrogen oxide having been removed, and supplies the generated turbine-driving steam to a steam turbine.
 10. The exhaust gas treatment device according to claim 1, wherein a heating unit configured to heat the integrated combustion exhaust gas is provided on a front stage of the nitrogen oxide removal unit, the integrated waste heat recovery unit generates the turbine-driving steam by using the waste heat of the integrated combustion exhaust gas heated by the heating unit, and supplies the generated turbine-driving steam to the steam turbine.
 11. The exhaust gas treatment device according to claim 9, further comprising: a control unit configured to measure the temperature and gas flow rate of the integrated combustion exhaust gas introduced into the nitrogen oxide removal unit, and control at least one of an amount of a fuel supplied to a combustor in the power generation facility and an amount of the steam supplied to the steam turbine, based on the measured temperature and gas flow rate.
 12. The exhaust gas treatment device according to claim 1, wherein the power generation facility includes an existing power generation facility.
 13. A exhaust gas treatment method comprising the steps of: removing nitrogen oxide in an integrated combustion exhaust gas into which a first combustion exhaust gas and a second combustion exhaust gas are integrated, the first combustion exhaust gas being discharged from a power generation device with waste heat of the first combustion exhaust gas having been recovered by a waste heat recovery unit which is provided to a first exhaust gas flow path, and the second combustion exhaust gas flowing through a second exhaust gas flow path which is provided to be connected between a front stage and a downstream stage of the waste heat recovery unit on the first exhaust gas flow path with a temperature of the second combustion exhaust gas being higher relative to the first combustion exhaust gas from which the waste heat has been recovered by the waste heat recovery unit; recovering waste heat of the integrated combustion exhaust gas with the nitrogen oxide having been removed; and recovering CO₂ in the integrated combustion exhaust gas by a CO₂ absorbing liquid, the waste heat of the integrated combustion exhaust gas having been recovered.
 14. An exhaust gas treatment method comprising the steps of: removing nitrogen oxide in an integrated combustion exhaust gas into which a first combustion exhaust gas and a second combustion exhaust gas are integrated, the first combustion exhaust gas being discharged from a first power generation device with waste heat of the first combustion exhaust gas having been recovered by a waste heat recovery unit which is provided to a first exhaust gas flow path, and the second combustion exhaust gas being discharged from a second power generation device and flowing through a second exhaust gas flow path with a temperature of the second combustion exhaust gas being higher relative to the first combustion exhaust gas from which the waste heat has been recovered by the waste heat recovery unit; removing nitrogen oxide in the integrated combustion exhaust gas into which combustion exhaust gases are integrated, the combustion exhaust gases being discharged and flowing through a plurality of exhaust gas flow paths at least one of which is provided with a waste heat recovery unit that recovers waste heat of the combustion exhaust gas; recovering waste heat of the integrated combustion exhaust gas with the nitrogen oxide having been removed; and recovering CO₂ in the integrated combustion exhaust gas by a CO₂ absorbing liquid, the waste heat of the integrated combustion exhaust gas having been recovered. 